(1) Field of the Invention
The present invention relates to a non-rigid vinyl chloride polymer resin composition having excellent weatherability, impact resistance and moldability.
(2) Description of the Related Art
Vinyl chloride polymer resins are widely used as general-purpose resins, but their mechanical properties are not completely satisfactory. A vinyl chloride polymer resin (hereinafter referred to as "PVC") has poor impact strength, especially poor notched impact strength. Accordingly, various methods for improving the poor impact strength of PVC have heretofore been proposed.
For example, there are known a method in which an MBS resin obtained by graft-polymerizing a methacrylic acid ester and an aromatic vinyl compound into a conjugated diene elastomer is blended with PVC and a method in which an ABS resin obtained by graft-polymerizing a vinyl cyanide compound and an aromatic vinyl compound into a conjugated diene elastomer is blended with PVC.
Furthermore, as the composition having an improved weatherability, various compositions have been proposed which comprise PVC blended with a copolymer obtained by graft-polymerizing an alkyl ester of methacrylic acid, an aromatic vinyl compound and a vinyl cyanide compound onto a rubbery elastomer composed of a saturated polyacrylic acid alkyl ester.
The copolymer obtained in the former method contains many double bonds in the main chain of the elastomer component, and therefore, when the copolymer is used outdoors for a long time, chalking and reduction of the impact resistance tend to occur. Accordingly, the composition of the former type is not suitable for outdoor uses. A composition obtained by blending the copolymer of the latter method with a non-rigid PVC comprising a plasticizer has a good weatherability, but when this resin composition is molded and processed, the tensile elongation at a high temperature is insufficient and the moldability is reduced. Therefore, application of the latter type copolymer to a non-rigid vinyl chloride polymer resin is very difficult in practice.